You’re a private detective. You’ve been called on a Saturday morning to urgently help a wealthy family solve a puzzle setup in their mansion by a psychopath.
You arrived at the mansion and saw the distressed family surrounded by police, friends and family. All trying to solve the puzzle.
You were greeted by a friend of the family (the person who called upon your help) and handed a copy of a note written by the psychopath.
With the note in your hand, you entered the living room, where the psychopath setup his/her puzzle, and noticed the following:
The family’s cat is locked up inside a glass box.
The glass box has two buttons, red and green.
Next to the box is a small computer with a mic.
You looked down at the note in your hand and read the following message written by the psychopath:
There is enough oxygen in the glass box to last the cat 24 hours.
One of the two buttons safely unlocks and opens up the box.
The other button however releases a poisonous gas that instantly kills the cat.
Trying to open the box without pressing any buttons (e.g. breaking the glass, etc..), or pressing both buttons at the same time releases the gas which also instantly kills the cat.
I’ve placed a computer with a mic that could hear and answer only one “yes/no” question (i.e. it can only answer with either the word “yes” or “no”).
The computer knows which of the two buttons unlocks and opens the box and which releases the gas.
You could ask the computer one question to help you solve the puzzle, but there is a catch.
The computer I placed here is actually one of two computers that I’ve built myself.
One of the two computers that I’ve built is designed to always tell the truth, while the other is designed to always lie.
However, I forgot which one of the two computers I’ve placed here, so it could be the liar or the truth teller.
Anyway, you have only one “yes/no” question to ask the computer. Use it wisely.
After reading the note, you now have a full understanding of the puzzle.
How would you solve it to help save the cat? What would your question to the computer be?
The computer answers only questions that could be answered with either the word “yes” or “no”.
it can answer “Is today Saturday?”
it cannot answer “What day of the week is today?”